The present invention relates to the testing and treatment of down hole formations in oil wells, and, more particularly, to a single trip method for conducting drill stem testing and acidizing and a well tool for use therein.
Drill stem testing provides an extremely accurate method of evaluating down hole formations. In fact, other than actual production from a completed well, drill stem or formation testing is the most reliable technique known for evaluation of the producing capabilities of formations. Procedures and apparatus for carrying out the testing are well documented in the literature. Briefly, the procedure involves opening a section of the well bore, in either open or cased hole, to atmospheric or reduced pressure. To accomplish this, the formation is isolated by a packer which supports the hydrostatic pressure load of the well fluid in the annulus surrounding the tool string. The formation is then exposed through a suitable valving system to atmospheric pressure in the drill pipe such that the formation's ability to produce fluid can be determined.
Acidizing and surfactant treatment is also a widely used and valuable technique. In conventional acidizing, a fluid such as hydrochloric acid is introduced, under pressure, into the formation to stimulate production from the formation.
It frequently occurs that many of the formations that are subjected to conventional drill stem testing are of a nature such that acidizing would convey valuable information as to what the producing capabilities of the formation would be if the well were completed. Presently, the most commonly used procedure for drill stem testing and acidizing requires two trips into the well, i.e. one trip for the drill stem testing and a separate trip for the acidizing. It will be readily apparent that such a procedure, requiring dual trips, is quite time consuming and, additionally, is quite costly.
While single trip methods of conducting drill stem testing and acidizing are known, they involve the use of valving systems in the tool string which are operated by relative rotation of the operating string. Such valving systems are relatively complicated and expensive. Additionally, rotation of the tool string necessary to actuate the valving may result in unseating of the packer. Accordingly, a method and apparatus which would permit single trip formation testing and acidizing without the necessity for string rotation is highly desirable.